Optional output directory only for test

We use Gradle 1.11 with the eclispe-wtp plugin. Everytime I do a “Refresh All” in eclipse my classpath entries will be overwritten which is not unexpected. The problem is that I use a different output folder for the test classes. (Eclispe: Properties->Java Build Path -> Source tab -> checkbox “Allow outputfolders for source folders” is clicked and the output folder is set to testbin for the src/test/java and src/test/resource

What I would like to do is configure gradle in the way this constellation will stay after a “Refresh All”. According to the documentation I can changed the defaultoutputDir but only general and I could not figure out how to set the output folder for my test classes to testbin.

The line in the eclipse .classpath file looks like

Additinally the compiled testclasses are also included in the Deployment Assembly which I have to remove them after every “refresh all”. Also this problem I would like to solve with gradle but have no idea how.

Thanks for helping